Enhancing the mechanical properties of guanosine-based supramolecular hydrogels with guanosine-containing polymers

We demonstrate that multivalent, polymeric 8-methoxyguanosine derivatives based on poly(dimethylacrylamide) can enhance the mechanical properties of the low molecular weight hydrogelator 8-methoxy-2′,3′,5′-tri-O- acetylguanosine at biologically relevant salt concentrations. It is proposed that these nongelling polymeric derivatives, under the conditions studied, can result in a significant enhancement of these supramolecular gels (e.g., for gels containing 1 wt % gelator G′ can be increased from ca. 2000 Pa with no additive to 80 000 Pa) by acting as supramolecular cross-linking units. Two competing mechanisms appear to play a role in these cogels. At low polymer concentrations the guanosine-containing polymers tend to act more as solubilizing agents for the gelator, thus weakening the gels, while at high guanosine-containing polymer concentrations the gels show a marked enhancement in mechanical properties consistent with them acting as supramolecular cross-linking agents. As such, the thermomechanical properties of these cogels depend on both the polymer:low molecular weight gelator ratio and the number of 8-methoxyguanosine repeat units present in the polymer additive. Thus, these polymeric guanosine-based additives impart the ability to tailor both the modulus and shear sensitivity of the gels. For example, cogels with a modulus ranging between ca. 95 and 80 000 Pa can be obtained through judicious selection of the type and amount of polymer additive.